Pseudolambrus bato, Tan, 2008

Tan, S. H., 2008, A new species of Pseudolambrus (Crustacea: Brachyura: Parthenopidae: Parthenopinae) from Panglao, Bohol, the Philippines, Zootaxa 1731 (1), pp. 63-68 : 64-67

Pseudolambrus bato sp. nov.

( Figs. 1 , 2 )

Material examined. HOLOTYPE: NMCR, female (31.30 x 21.58 mm), Philippines, Panglao Island , Alona reef, PANGLAO 2004 expedition, stn N3, 9° 32.9' N 123°46.6' E, 25–30 m, baited traps, 7 June 2004.

Description. Carapace sub-triangular, wider than long, ratio CW/CL = 1.45. Surface rugose, with numerous granular knob-like tubercles. Juncture between mesogastric and epigastric regions excavated, pit smooth. Epibranchial regions with large projection on lateral margins.

Rostrum tuberculated, tip bilobed, bluntly rounded, directed downwards; dorsal surface with a semi-circular pit, base of pit smooth. Frontal region tuberculated, dorsal surface with a sub-horizontal, circular pit, base of pit smooth. Orbital region rugose. Protogastric region convex; mesogastric region with median, oval, low tubercle; metagastric region low. Cardiac region depressed. Intestinal region raised, continuous with posterior margin. Hepatic region slopes towards hepatic margin. Epibranchial region raised, junction between anterior and posterior epibranchial region with tall conical tubercle, tubercle rugose. Mesobranchial region slightly elevated. Metabranchial regions concave.

Orbital margin rugose, supraorbital suture indistinct; inner orbital margin slightly elevated; mid-orbital depression present; lateral orbital margin slightly elevated. Hepatic margin descending almost vertically, tip blunt, consisting of a cluster of tubercles, no distinct tooth. Epibranchial margin strongly convex; first anterior epibranchial tooth beneath hepatic notch, 11 teeth, each tooth flattened dorsal-ventrally, tooth dorsal surface rugose, anterior teeth distinct, posterior ones tend to merge and form flattened margin near end of epibranchial margin. Mesobranchial region with distinct tooth, tooth flattened dorso-ventrally, surface tuberculated, with raised median ridge. Posterior margin sinuous, tuberculate, tubercles rounded.

Epistome with small central depression, posterior region in depression with two low ovoid lobes; anterior and posterior margins with distinct ridge. Sub-hepatic region surface tuberculated, with deep channel beneath, channel runs from beneath eye to posterior hepatic margin. Hepatic notch present, deep.

Eyes mobile, eyestalks smooth, short; tip of cornea with small tooth; orbital fossa deep, about 80% of cornea concealed when eye folded away.

Antennal article one sub-trapezoidal, surface irregular, mobile. Antennal article two sub-rectangular, surface irregular, with prominent tubercle near outer margin, immobile, fixed to epistome and suborbital margin. Antennal article three rectangular; with three small distal tubercles; mobile. Antennal article four rectangular; lateral margins each with two teeth, teeth triangular, teeth tips blunt; mobile. Antennal flagellum about one and a half times length of articles three and four combined.

Antennular article one sub-trapezoidal; surface irregular; inner margin raised, appearing ridged. Antennular article two long and slender; about same length as antennular article one; surface smooth; with a central tubercle. Antennular article three long and slender; about same length as antennular article two; surface smooth.

Third maxilliped basis-ischium medial edge dentate; with four small clusters of setae behind medial edge, setae long; central longitudinal cavity present. Merus squarish; surface tuberculate; distal diagonal ridge present, ridge with three tubercles, anterior tubercle smallest, posterior tubercle largest; distolateral corner of merus partially conceals tip of third maxilliped exopod. Carpus, propodus and dactylus of endopod decrease in size distally; propodus and dactylus exposed, not hidden behind merus.

Cheliped merus short, completely hidden under carapace; inner margin dentate, a large tooth present on distal two-fifth region, tooth tuberculate; outer margin proximal three-quarter region with 6 teeth, distal onequarter region with a flatten protrusion. Cheliped carpus surface tuberculate; upper margin with one median sub-acute tooth, tooth tuberculate. Right cheliped propodus about twice the size of left cheliped propodus; outer margin outer margin with two lobes, lobes broad, low; inner margin dentate, with about 8 teeth, teeth about equal in size. Right dactylus upper margin dentate; inner margin dentate, medial region with three broad, triangular teeth. Right cheliped pollex inner margin dentate, inner most tooth largest, molariform. Left cheliped propodus with two very low, indistinct lobes; inner margin dentate, with about 8 teeth, teeth about equal in size. Left cheliped dactylus upper margin dentate; inner margin dentate, with about four triangular teeth. Left cheliped pollex inner margin dentate, teeth triangular.

Ambulatory legs decrease in length posteriorly. P2 merus, carpus, propodus upper margins dentate; merus lower margin dentate; carpus lower margin smooth; propodus lower margin slightly tuberculate; dactylus pubescent, setae low. P3 merus upper margin dentate, about 8 teeth present; carpus upper margin dentate, three teeth present; propodus upper margin dentate, one tooth present; merus lower margin dentate, 4 teeth present; carpus lower margin with one small, median tubercle; propodus lower margin slightly tuberculate; dactylus pubescent, setae low. P4 merus upper margin dentate, about 8 teeth present; carpus upper margin dentate, 3 tooth present, teeth flattened laterally, distal-most tooth lobate; propodus upper margins dentate, with 1 tooth, teeth flattened laterally; merus lower margin dentate, about 5 teeth present; carpus lower margin with one small, median tubercle; propodus lower margin slightly tuberculate; dactylus pubescent, setae low. P5 merus upper margin dentate, about 7 teeth present; carpus upper margin dentate, 2 teeth present, teeth lobate, flattened laterally; propodus upper margins dentate, with 1 lobate tooth, teeth flattened laterally; merus lower margin dentate, with two distinct lobate teeth; carpus lower margin with one lobate tooth; propodus lower margin with 2 lobate teeth, proximal tooth smaller; dactylus pubescent, setae low; upper margin slightly tuberculate.

Abdominal segments all free in female holotype; surface heavily tuberculate. Abdominal locking mechanism barely effective in female holotype; tubercles on thoracic sternite 5 well developed; sockets on abdominal segment 6 present. Telson sub-triangular, slightly wider than long, tip bluntly rounded.

Female holotype gonopore oval; situated mid-way on sternite 6; not raised above sternal surface. Male gonopod unknown .

Etymology. The species name, bato, is derived from the Tagalog and Cebuano word for rock or stone, in allusion to this crab resembling a piece of rock when it was first collected. Used as a noun in apposition.

Remarks. When this specimen was first obtained in a trap, there was little doubt that it was a new species because of its remarkable carapace features. The species superficially resembles a member of the Daldorfiinae due to the carapace being wider than long, and the cheliped merus being totally hidden beneath the carapace ( Tan & Ng, 2007b). No known parthenopine species has such a carapace ratio. On closer examination, it was found that the specimen did not belong in the Daldorfiinae because the length and width of the second antennal article is about half that of the first antennular article, i.e. it is a typical parthenopine (see Tan & Ng, 2007a).

The cheliped of the specimen suggested that this species belongs in the genus Pseudolambrus . The relatively short cheliped initially caused doubt with this placement. However, further investigations revealed that in Pseudolambrus , it is common to find female specimens having shorter chelipeds than the males. As such, the relatively short cheliped of this species is here attributed to sexual dimorphism.

Currently, 15 species of Pseudolambrus species are recognized by Ng et al. (2008) viz. Pse. beaumonti ( Alcock, 1895) , Pse. bicornis ( Flipse, 1930) , Pse. bidentatus ( Flipse, 1930) , Pse. bispinosus ( Rathbun, 1902) , Pse. calappoides ( Adams & White, 1849) , Pse. confragosus ( Calman, 1900) , Pse. harpax ( Adams & White, 1848) , Pse. hepatoconus ( Flipse, 1930) , Pse. lobatus ( Flipse, 1930) , Pse. longispinosus ( Flipse, 1930) , Pse. planus ( Rathbun, 1911) , Pse. saishoi Takeda, 1977 , Pse. sandrockii ( Haswell, 1880) , Pse. sundaicus Ng & Rahayu, 2000 , and Pse. tarpeius ( Adams & White, 1849) (see also Tan, 2004). This new species possess a bilobed rostrum that is similar to Pseudolambrus species like Pse. calappoides ( Adams & White, 1849) and Pse. confragosus ( Calman, 1900) . In addition, the external margin of the major cheliped manus has two broad lobes that could be found in Pseudolambrus species like Pse. hepatoconus ( Flipse, 1930) . However, no known Pseudolambrus species has such large lateral protrusions on the carapace and has wider carapace width than the carapace length. As such, these two characters easily distinguish Pse. bato from all other Pseudolambrus species.

Tan & Ng (2007a) reviewed the genera in the Parthenopinae and concluded that the genus Pseudolambrus should be restricted for species in the Indo-Pacific. Two species from the eastern Pacific and an Atlantic species formerly placed in Pseudolambrus are now transferred to Ochtholambrus Tan & Ng, 2007 , viz. O. excavatus ( Stimpson, 1871) , O. stimpsoni ( Garth, 1958) and O. pulchellus (A. Milne-Edwards, 1868) . In describing Ochtholambrus, Tan & Ng (2007a) listed four species in the genus, O. excavatus ( Stimpson, 1871) (designated type species), O. stimpsoni ( Garth, 1958) , O. pulchellus (A. Milne-Edwards, 1868) , and O. triangulus ( Stimpson, 1860) . However, in their comments about the new genus, Tan & Ng (2007a: 108) wrote “The new genus contains two eastern Pacific Pseudolambrus species , sensu Rathbun (1925) and Garth (1958) (excluding Lambrus triangulus Stimpson, 1860 ), as well as the Atlantic Lambrus pulchellus A. Milne- Edwards, 1868. Lambrus triangulus differs from Ochtholambrus in the differently shaped carapace and male abdomen and telson. In addition, the carapace of L. triangulus is also more pilose than Ochtholambrus species , and is here referred to a new genus, Pisolambrus .” The inclusion of Lambrus triangulus Stimpson, 1860 , in Ochtholambrus Tan & Ng, 2007 , is a mistake, and should be transferred to Piloslambrus Tan & Ng, 2007 (type species Lambrus depressiusculus Stimpson, 1871 ), instead. Two alternate spellings for Piloslambrus were used in that paper, “ Pisolambrus ” ( Tan & Ng, 2007a: 108) and “ Pilolambrus ” ( Tan & Ng, 2007a: 119), and both are typographical mistakes.

Figures

FIGURE. 1. Pseudolambrus bato sp. nov, NMP, female (31.30 x 21.58 mm). A, whole specimen. B, right-side profile. C, anterior view. D, posterior view. E, right major cheliped. F, left minor cheliped.

FIGURE. 2. Pseudolambrus bato sp. nov, NMP, female (31.30 x 21.58 mm). A, epistome and external mouthparts. B, abdomen. C, ventral view of posterior margin. D, right P5.